PHILADELPHIA — It was his biggest miss as a Celtic and Courtney Lee knew it. This wasn’t a regular miss in a regular loss. Lee missed everything and it exemplified his struggles in Boston.

With the Celtics ahead by a point in the final minute of overtime, Rajon Rondo found an open Lee in the corner, his favorite spot on the floor. Lee gathered the pass and fired a 23-footer that never had a chance, the ball soaring 3 feet over the basket for an embarrassing airball.

Evan Turner came back and cashed in a 13-footer, which was the deciding margin in the Celtics’ 95-94 overtime loss to the Philadelphia 76ers. For Lee, it was a disheartening moment, especially given his shooting struggles.

A career 38.5 percent 3-point shooter entering this season, Lee is 7 of 27 from beyond the arc with the Celtics and has missed a series of pivotal shots. Friday’s was a crusher, leaving him to ponder his shortcomings after the game.

“I know Doc [Rivers] talked to the media and probably said it was unfair that I was sitting like 12 minutes [before the shot], but it doesn’t matter,” Lee said. “NBA players get paid to play this game. At least, I should have hit the rim and given us a chance to get the offensive rebound. I didn’t do that so I’m very disappointed in myself.

“I know when I took the shot, I was stiff so I overshot it to try to make sure it got there. But I put a little too much oomph in it. I have to be able to make the shot or hit the rim, at least.”

Lee has been playing well of late, providing defensive spark, but his offense has yet to meet expectations. He began the season as the starting shooting guard but lost his job to Jason Terry. He was 4-for-22 shooting from the 3-point line in November and has hit just one 3-pointer in 10 home games.

Friday was an opportunity to seize the moment, seal an important victory with a clutch shot, but it wasn’t even close.

“The confidence is always going to be there because I’ve been playing basketball for a while,” he said. “I can’t count or recall how many times I’ve shot an airball but you’ve just got to continue to work and keep practicing, that’s all.”

Rivalry renewed

The 76ers’ recent resurgence under coach Doug Collins has been good for the city and the club has reinvigorated its rivalry with the Celtics, making this rare two-game, back-to-back set the most interesting stretch of the early season.

The series started in typical fashion with the 76ers’ dramatic overtime win. Philadelphia’s athleticism and physicality make it a difficult matchup for the finesse Celtics, so the two games should provide an arduous test, one Rivers relishes.

“I like it, I’ve always liked it, I think most coaches don’t like it,” he said. “I just always thought that it’s very competitive from a playing standpoint when you play the same team back-to-back the games become very competitive, almost chippy. I like it.

“The downside to it is it’s very, very hard to win both games. I think that’s why most coaches don’t like it. When it’s two good teams, it’s even more dangerous because you could lose both games, the whole thing is hard. I like it but I can see why most don’t.”

Feeling full

The Celtics still have one roster spot open but Rivers said there hasn’t been much discussion about filling it. An NBA source said this week that the club was considering veteran center Erick Dampier.

“I’m good; obviously if there was somebody out there we’d look,” Rivers said. “I can tell you I haven’t had any conversations with [team president] Danny [Ainge] about anyone basically since the season started. We haven’t looked at anyone but if there’s someone out there, give me a call.”

Better now

Leandro Barbosa and Jared Sullinger, both of whom had been battling flu-like symptoms, were healthy enough to play Friday. Sullinger logged 13 minutes and pulled down five rebounds but Barbosa did not play . . . The 76ers were without Nick Young (hyper-extended left big toe), who burned the Celtics for 10 points in 18 minutes Nov. 9. Royal Ivey (groin strain) and Kwame Brown (stomach virus) were also out . . . The 76ers are 2-7 when they shoot a worse percentage than their opponents . . . After posting just one double-double last season, Thaddeus Young posted his fifth of the season with 17 points and 12 rebounds Friday.